1. Field of the Invention
This disclosure generally relates to the field of automatic data collection (ADC), for example, data acquisition via machine-readable symbols and readers, radio frequency identification (RFID) tags and readers, magnetic stripes and readers, and more particularly relates to providing communications in potentially hazardous environments, for example, between one or more ADC readers and one or more host computing systems.
2. Description of the Related Art
The ADC field includes a variety of different types of ADC data carriers and ADC readers operable to read data encoded in such data carriers. For example, data may be encoded in machine-readable symbols, such as barcode symbols, area or matrix code symbols and/or stack code symbols. Machine-readable symbols readers may employ a scanner and/or imager to capture the data encoded in the optical pattern of machine-readable symbol. RFID tags may store data in a wirelessly accessible memory, and may include a discrete power source, or may rely on power derived from an interrogation signal. RFID readers typically emit a radio frequency (RF) interrogation signal that causes the RFID tag to respond with a return RF signal encoding the data stored in the memory. Magnetic stripes encode data in patterns of magnetic particles. Such magnetic stripes are commonly, for example appearing on the back of credit, debit or gift cards. Magnetic stripe readers typically employ a magnetic reading head, with a slot through which the magnetic stripe is drawn. Other types of data carriers and readers exist, for example optical memory tags and touch memories.
Most ADC systems employ a number of ADC readers which may be distributed about one or more locations to collect data from the data carriers, and may employ one or more host computing systems that act as central depositories to store and/or process and/or share data collected by the ADC readers. In many applications, it is beneficial to provide wireless communications between the ADC readers and the host computing system. Wireless communications allow the ADC readers to be mobile, may lower the cost associated with installation of an ADC system, and permit flexibility in reorganizing a facility, for example a warehouse. ADC systems may employ wireless access points distributed throughout a facility to facilitate such wireless communications.
Some applications require the operation of ADC readers and other equipment in a potentially hazardous environment. For example, ADC readers may be placed in a combustible environment such as one with a high concentration of oxygen or other combustible gas, or one in which an unintentional leak of a combustible gas may occur. Test and certification laboratories provide intrinsically safe ratings warranting that equipment which such a rating cannot create a, spark that may ignite a potentially combustible environment. The testing and certification laboratories carefully review the equipment prior to providing such a rating, to ensure that such hazardous conditions cannot occur in either normal operation or in the presence of faults. Several devices are already available that isolate low voltage circuits and provide the intrinsically safe rating through supplemental protection circuits. There appears to be no such supplemental circuit currently available for RF devices. It would be highly desirable in the communications industry to be able to provide wireless communications in a potentially hazardous environment.